If you want to read more about Judo vs. Sambo, check Alexander Iatskevich's book. I'd type out his whole introduction, but I'm lazy. He mentions that there's a whole bunch of cross training (Judo-SOMBO), and that while Somboists made quite an impression on the Japanese, Japanese people have come over and won SOMBO championships too. (I'm just imagining some Russian guys being all "WHAT IS UP WITH THESE WACKY COLLAR AND ELBOW GRIPS? CAN'T THESE PEOPLE USE BELT GRIPS LIKE NORMAL PEOPLE?!")